Crystal Growth and Novel Quantum Transport of Topological Semimetals and La3Ir3O11

Author:Yang Jun

Supervisor:zhang chang jin


Degree Year:2019





Strong spin-orbit coupling(SOC)plays an important role in condensed matter physics in view of its prominent influence about electronic band structure and magnetic structure.In recent years,some novel quantum phenomena,like topological insulator state and quantum spin liquid,have been found in several mateials with strong SOC.Besides,charge density waves(CDW)arouse much interest due to its collective excitation mode which is akin to superconductivity,so it is worth of exploring its evolution and relationship with other multiple interactions.Our thesis focuses on the growth,transport and magnetic properties of several typical materials with strong SOC,including TaP,La3Ir3O11,MoP and TaSe3.The thesis is divided into six chapters.In chapter one,we briefly introduce the definition and classification of spin-orbit coupling,then present two categories materials with strong SOC:the topological materials,spin-orbit coupling Mott insulator.Whereafter,we present a SOC induced effect:spin Hall effect.Finally,we introduce several mechanisms and applications of CDW.In chapter two,we introduce the giant planar Hall effect(PHE)and anisotropic magnetoresistance(AMR)observed in Weyl semimetal TaP,which mainly come from large anisotropic orbital magnetoresistance rather than chiral anomaly.The current jetting effect induced by high carrier mobility of TaP not only deforms the PHE and AMR curves but also leads to a double-peak structure and negative resisitivity in the AMR curves.In chapter three,we study the novel properties of single crystal La3Ir3O11,it is a typical spin-orbit coupling induced Mott insulator with a gap around 34 meV,which is verified by our DFT calculations.The magnetic susceptibility shows some anomalous fetures,such as a Curie-Weiss paramagnetism in the low temperature,a linear-temperature dependence above 70 K and a hump at 500 K.Then we use a new theoretical model established on the basis of competing nearest-neighbor and next-nearest-neighbor interactions to interpret those futures well.In chapter four,we presents spin pumping experiments at topological semimetal MoP/Py bilayer.The obtained spin-Hall angle θSHE of MoP is 0.0031,together with a large spin Hall conductivity 4.5562×104h/2e(Ω m)-1 at room temperature.The special magnetic field angle dependence of the inverse spin-Hall voltage demonstrates its spin Hall effect is dominated by surface Fermi arcs.In chapter five,we study the growth,transport,Raman spectroscopy and magnetic susceptibility of TaSe3 nanowires.For the first time,a CDW transition at Tp=65 K was observed in TaSe3 nanowire with 300 nm width.Detailed Raman spectroscopy data suggests the occurrence of CDW transition is attributed to the enhanced quasi-ID character and electron-phonon coupling by reducing dimensionality.In chapter six,we show the the summary and prospects of this thesis.